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This probabilistic forecast is issued by the Middle Atlantic River Forecast Center.
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Experimental Short Range Forecast Uncertainty (AHPS) - External Links: Product Description Document | Customer Survey
About this graph
Forecasts for the Potomac River near Washington DC (Little Falls) are issued routinely year-round.
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Zoom Level:14
Flood Categories (in feet)
Major Flood Stage: 14
Moderate Flood Stage: 12
Flood Stage: 10
Action Stage: 5
Low Stage (in feet): 0

Historic Crests
(1) 28.10 ft on 03/19/1936
(2) 26.88 ft on 10/17/1942
(3) 23.30 ft on 04/28/1937
(4) 22.03 ft on 06/24/1972
(5) 19.29 ft on 01/21/1996
Show More Historic Crests

(P): Preliminary values subject to further review.

Recent Crests
(1) 11.01 ft on 09/29/2018
(2) 10.85 ft on 09/11/2018
(3) 12.38 ft on 06/05/2018
(4) 11.70 ft on 05/18/2014
(5) 10.33 ft on 10/31/2012
Show More Recent Crests

(P): Preliminary values subject to further review.

Low Water Records
Currently none available.
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Gauge LocationGauge Map Marker
Latitude/Longitude Disclaimer: The gauge location shown in the above map is the approximate location based on the latitude/longitude coordinates provided to the NWS by the gauge owner.
Flood Impacts & Photos Collapse
If you notice any errors in the below information, please contact our Webmaster
17 Water overflows the overlooks at Great Falls National Park and approaches the lower level of the visitors center. Most of the C&O Canal towpath downstream of Pennyfield is flooded.
15 Most of the C&O Canal towpath from Pennyfield downstream is flooded.
14 Significant portions of the C&O Canal towpath are flooded. The Blockhouse Point Park is flooded. Water reaches the retaining wall at Overlook 1 at Great Falls National Park but does not overtop it.
12 The C&O Canal overflows at the Great Falls Tavern. Water covers the towpath in many areas.
11.5 Water covers the towpath in multiple spots between the Washington Aqueduct Dam and Pennyfield Lock, mileposts 15 to 19 on the C&O Canal.
11 Water covers the towpath between Swains Lock and Pennyfield Lock, mileposts 17 to 19 on the C&O Canal.
10 Water begins to overflow the banks into low lying areas on the Maryland side of the river near Little Falls.
9 Several trails on both sides of the river between Great Falls and the Chain Bridge are flooded and will be closed.
7 Upper portions of the River Trail at Great Falls National Park begin to flood and will be closed.
5.5 Water begins to affect portions of the Billy Goat Trail between Great Falls and Carderock. These trails may be closed.
5 Portions of the Potomac Heritage Trail begin to flood.
4.5 The river reaches danger level for boaters, as defined by the State of Maryland. Conditions for boating will be extremely hazardous.
3.5 The river reaches caution level for boaters, as defined by the State of Maryland. Fast moving water and changing currents will be experienced.

Other Real-time and/or Archive Data Sources:

Additional Information Collapse
Potential River Levels - Used to
Potential River Levels
Used to Estimate the Chance of Flooding and the Range of Possible River Levels
3 Day (SREF) 7 Day (NAEFS) 7 Day (GEFS)
SREF Ensemble NAEFS Ensemble  GEFS Ensemble 

Note: Use the official hydrograph at the top of this web page for river levels within the next 48 hours.

See the Product Description Document link for more details on the interpretation of the 3,7 day graphics. 

Click individual graphics to enlarge.

Collaborative Agencies Collapse
The National Weather Service prepares its forecasts and other services in collaboration with agencies like the US Geological Survey, US Bureau of Reclamation, US Army Corps of Engineers, Natural Resource Conservation Service, National Park Service, ALERT Users Group, Bureau of Indian Affairs, and many state and local emergency managers across the country. For details, please click here.
NWS Information
National Weather Service
(Baltimore/Washington) Sterling Weather Forecast Office
43858 Weather Service Rd.
Sterling, VA 20166
(703) 996-2200
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Page last modified: 5-Mar-2019 11:43 PM
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